Generally the cruise company offers a dive day trip. Who are they using?
Some time ago, I learned that the price for the cruise day trips was very close to the price booking on your own. Out of BC, it is a serious advantage to be booking with the cruise ship. They will wait for you if the dive boat breaks down if you've booked with them. They won't, if you've booked on your own.
If I recall correctly, Norwegian Cruiselines was taking people out to Glover's for the day. Sounded pretty good to me.